Chainsaw is the main dangerous equipment in forest work which has great potential damage to felling crew. Management of the risks arising from working with a chainsaw depends on the assessment of its risks. There is still no suitable method for evaluating the risk of work with this device. Generally, the risks of working with chainsaw are presented without rating. This study was designed to rank the dangers of working with this device. For investigation of dangers related to chainsaw during tree felling Job safety analysis was used. During these phase, comment of chainsaw men, felling operation supervisors, harvesting experts, and Work safety specialists working in forestry plan in Caspian forest were used. Then, the risk assessment criteria were investigated by Delphi method with help of felling workers, forest watershed managers, forestry specialist, and university professors. Results were Conclusion by forest safety experts. Finally, the risk ranking was done using the Fuzzy Topsis method. Risk assessment criteria were obtained using the Delphi method. Ranking of hazards with Fuzzy Topsis was determined. The results of this study showed that the dangerous trees, butt log and chainsaw kickback are the most important risks of chainsaw operation. This study enhanced the ability of risk detection of felling operation with chainsaw and correct risk assessment criteria identification with ranking of felling hazards. The final analysis resulted in rating the dangers of working with this device that it can reduce the incidents caused by working with this device by compiling the appropriate safety instructions.